Improved screw-tap



@anni @tijm WALTER K. FOSTER, 0F CAMBRIDGEPORT, MASSACHUSETTS.

' i LenersPatmtNo. 83,371,6mm1 0cb`wr'27,1s6s.

IMPROVED SCREW-TAP. v

f-w--O-Qo--- The Schedule referred to in these Letters Patent and making part of the Barrie.

To all persons to whom these presents may come:

Be it known that I, WALTER K. FOSTER, of Gambridgeport, of the county ofL Middlesex, and State of Massachusetts, have invented a new and useful Improvement in Serew'laps; and do hereby declare the same to be fully described in the following specification', andrepresented inI the accompanying drawings, of which- Figure l denotes a front elevation,

Figure 2, a vertical section, and

Figure 3, a horizontal and transverse seotionof screw-tap' provided with my improvement. A

In carrying out my invention, I take a cominon screwltap,-A1 and form in it, from its head, and down along in linqof' its axis, or' about so, an oiling-passage, a, from which I lead a hole, b, laterally through the tap to the upper part of one of its series or ranges. c c c c, of screwcutters. I also form in suoh range a groove, d, to ex. tend down therein, fror the said hole, to or nearly to l the bottom of the rang'e.

For the purposes of my invention, the tap may be tubuiar, or be bored through from end to end, in which case I usually insert in -the bore or hole a plug, having its upper end on a level with, or somewhat lbelow, the inner end of the lateral passage b, in order that oil, after having been poured into the upper end of the bore or passage a, may loW through the hole b upon the range of cutters, or into the groove made down therein.

When a screw-tap is so made, or proded with my improvement, it Will be an easy matter to oil its cutters A vvhle it may be in the act of cutting a female screw.

To accomplish this, the lubricating-Hind is to be poured Whatwould be neoessary were the tap unprovided with the improvement.

' An equivalent for the passage a b'would be a single passage, leading from the upper end of the screw-tap obliquelythrough the shank, and out through one of the ranges of cutters.

If desirable, there may be more than one lateral pas sage leading from the main oiling-passage to the outside of the tap. The lateral passage may have a very small diameter in comparison to that of the vertical passage, which may be so large as to constitute a reservoir for holding oil, inI which case, if desirable, a plug may be fixed on the mouth of the passage c, so as to cause the oil to weep from time to time, in a very small quantity,V

from the discharge-passage. The said plug may be a screw, screwed into the top of the oil-receptacle.

What I claim as my invention is- The arrangement of the main and lateral oiling-passages d b, and the groove d, in one of the ranges of screw-cutters, theA Whole being substantially as described.

W. K. FOSTER; Witnesses:

R. H. EDDY, F. P. HA'LE, Jr. 

